Rails的：用的has_many额外的细节？ [英] Rails: has_many with extra details?

问题描述

虽然我不是一个完整的Ruby / Rails的福利局，我还是pretty的绿色，我试图找出如何构建一些模型关系。我能想到的最简单的例子是食谱做饭的想法。

一个配方由一种或多种成分和每种成分的相关数量。假设我们有一个主列表中的所有成分的数据库。这表明两个简单的模型：

 类成分＆LT;的ActiveRecord :: Base的
  ＃成份名称，
结束

一流的配方＆LT;的ActiveRecord :: Base的
  ＃配方名称等。
结束
 

如果我们只是想配方与成份相关联，这是因为simpling如添加适当的 belongs_to的和的has_many 。

但是，如果我们要与这种关系的其他信息联系起来呢？每个配方有一个或多个成分，但我们要指出的成分的量。

什么是Rails的方式来模拟？它是沿着的has_many的东西线，通过？

 类成分＆LT;的ActiveRecord :: Base的
  ＃成份名称
  belongs_to的：recipe_ingredient
结束

类RecipeIngredient＆LT;的ActiveRecord :: Base的
  HAS_ONE：成分
  HAS_ONE：食谱
  ＃ 数量
结束

一流的配方＆LT;的ActiveRecord :: Base的
  的has_many：recipe_ingredients
  的has_many：配料，：通过=＆GT; ：recipe_ingredients
结束
 

解决方案

配方和配料都有了属于一对多的关系，但是你想存储更多信息的链接。

您正在寻找本质上讲是一个丰富的连接模型。但是，一个has_and_belongs_to_many关系是不够灵活，无法存储您所需要的其他信息。相反，你将需要使用的has_many：通过relatinship

这是我怎么会设置它。

菜谱列：说明

 类食谱＆LT;的ActiveRecord :: Base的
  的has_many：recipe_ingredients
  的has_many：配料，：通过=＆GT; ：recipe_ingredients
结束
 

recipe_ingredients列：recipe_id，ingredient_id，量

 类RecipeIngredients＆LT;的ActiveRecord :: Base的
  belongs_to的：食谱
  belongs_to的：成分
结束
 

成分列：名称

 类成分＆LT;的ActiveRecord :: Base的
  的has_many：recipe_ingredients
  的has_many：食谱，：通过=＆GT; ：recipe_ingredients
结束
 

这将为你在找什么做的基本的重新presentation。您可能需要验证添加到RecipeIngredients，以确保每个成分列出一次每个配方，并回调折叠重复到一个条目中。

While I'm not a complete Ruby/Rails newb, I'm still pretty green and I'm trying to figure out how to structure some model relationships. The simplest example I can think of is the idea of "recipes" for cooking.

A recipe consists of one or more ingredients and the associated quantity of each ingredient. Assume we have a master list in the database of all ingredients. That suggests two simple models:

class Ingredient < ActiveRecord::Base
  # ingredient name, 
end

class Recipe < ActiveRecord::Base
  # recipe name, etc.
end

If we just wanted to associate Recipes with Ingredients, that's as simpling as adding the appropriate belongs_to and has_many.

But what if we want to associate additional information with that relationship? Each Recipe has one or more Ingredients, but we want to indicate the quantity of the Ingredient.

What is the Rails way to model that? Is it something along the lines of a has_many through?

class Ingredient < ActiveRecord::Base
  # ingredient name
  belongs_to :recipe_ingredient
end

class RecipeIngredient < ActiveRecord::Base
  has_one :ingredient
  has_one :recipe
  # quantity
end

class Recipe < ActiveRecord::Base
  has_many :recipe_ingredients
  has_many :ingredients, :through => :recipe_ingredients
end

解决方案

Recipes and Ingredients have a has and belongs to many relationship, but you want to store additional information for link.

Essentially what you are looking for is a rich join model. But, a has_and_belongs_to_many relationship is not flexible enough to store the additional information you require. Instead you will need to use a has_many :through relatinship.

This is how I would set it up.

recipes columns: instructions

class Recipe < ActiveRecord::Base
  has_many :recipe_ingredients
  has_many :ingredients, :through => :recipe_ingredients
end

recipe_ingredients columns: recipe_id, ingredient_id, quantity

class RecipeIngredients < ActiveRecord::Base
  belongs_to :recipe
  belongs_to :ingredient
end

ingredient columns: name

class Ingredient < ActiveRecord::Base
  has_many :recipe_ingredients
  has_many :recipes, :through => :recipe_ingredients
end

This will provide a basic representation of what you're looking to do. You may want to add a validation to RecipeIngredients to ensure that each ingredient is listed once per recipe, and a callback to fold duplicates into one entry.

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